Process using activated electroless plating catalysts

ABSTRACT

A process and method for the formation of novel colloidal catalytic electroless plating compositions comprising the admixture of at least one primary colloid stabilizer which otherwise renders the colloidal dispersion highly stable however weakly active with at least one secondary colloid stabilizer (or reactivity modifier) thereby activating the colloidal dispersion to a more active state when used in the catalytic treatment prior to electroless (chemical) plating.

This is a division of application Ser. No. 941,044 filed Sept. 11, 1978,now U.S. Pat. No. 4,180,600, which is a continuation-in-part of U.S.application Ser. No. 820,904 filed Jan. 1, 1977 now U.S. Pat. No.4,131,699, which is a continuation of U.S. application Ser. No. 625,326filed on Oct. 23, 1975, now U.S. Pat. No. 4,048,354.

BACKGROUND OF THE INVENTION

In the plating of dielectric substrates by chemical (electroless)plating it is well known that suitable catalytic pretreatment is aprerequisite for effective electroless metal deposition. Such practicesare well known and accepted in the art.

In examining the prior art for catalytic pretreatment it appears thatwhile different procedures have been used, the incorporation of preciousmetals (e.g. palladium containing solutions) was common to allprocedures. One catalytic system of particular interest is the two stepprocess as disclosed in U.S. Pat. No. 3,011,920. In the processdisclosed, a colloidal solution composed of tin(II) and precious metalsalts, generally with hydrochloric acid, is used. The effective catalystis proposed to be a colloid of an elemental precious metal (e.g.palladium) stabilized by the excess stannous chloride present in themedium. While the system disclosed in U.S. Pat. No. 3,011,920 has beenquite popular in commercial practices, rising costs of precious metalsand miscellaneous product reliability problems have led to the quest fornew systems in which the use of precious metals, tin, as well ashydrochloric acid would be completely eliminated.

In meeting this objective it was found, as described in U.S. Pat. Nos.3,993,799 and 4,087,586 filed by the applicant herein, that colloidalsystems (metals, alloys, and compounds) based upon non-precious metalscould constitute the basis for new commercial plating processes. Basedupon the teachings disclosed in U.S. Pat. Nos. 3,011,920 and 3,993,799,the metals which are catalytic to electroless plating are evident. Morespecifically, it was found that colloids of non-precious metals(preferably, but not limited to, those selected from the group ofcopper, iron, cobalt, nickel and combinations thereof) may be used inthe direct replacement of the tin/palladium colloid followed by atreatment in a suitable reducing medium. In the reducing medium,reduction of the ionic portion of adduct (or surface of colloid) derivedthrough the adsorption from the colloidal medium takes place, resultingin active nucleating sites capable of initiation of the electrolessprocess. It is noted, however, that the reducing medium can be deletedsince most electroless plating baths contain at least one reducingagent. Accordingly, the present invention is applicable to both modes ofprocessing.

In reviewing the teaching disclosed in U.S. Pat. No. 3,993,799, it isrecognized that many of the inherent disadvantages associated with thepalladium based catalysts are eliminated. It is further recognized thatbased upon practices in this art, it is essential that any catalyticsystem should maintain its properties especially with storage (e.g.several months) and shipment under conditions of substantial temperaturefluctuations. It is thus highly desirable to have a medium in which goodcolloidal stability would be maintained, and at the same time havesufficient catalytic activity to be used in the plating process. I havegenerally observed that as one increases the stability, the activity isdecreased thereby making it difficult to meet both requirements in asingle system.

For example, I have observed that active plating colloids have generallyshown a limited stability (for long term storage purposes) due tocoagulation which takes place leading to precipitation, with change inparticle size and distribution during the coagulation process. Inaddition, I have noted that highly stable colloidal dispersions haveshown limited catalytic activity when used in accordance with U.S. Pat.No. 3,993,799 and moderate concentrations of reducing medium oractivating medium. Similar trends were also noted in U.S. Pat. No.3,948,048 on the interrelationship between reactivity and stability. Infact, in U.S. Pat. No. 3,958,048 some of the illustrated examples losttheir colloidal character and became true solutions within 24 hours.

It is thus an objective of this invention to provide both stable andactive colloidal dispersions which are useful in electroless platingprocesses as well as in other processes having the same prerequisites.While not wishing to be repetitious, the following are included hereinby reference: U.S. Pat. Nos. 3,011,920, 3,993,799, 3,958,048, 3,993,491,3,993,801, 4,087,586, and Ser. Nos. 625,326, 820,904, 833,905, 651,507and 731,212.

SUMMARY OF THE INVENTION

A method for preparing a novel catalytic colloidal composition useful inelectroless plating techniques comprises the step of admixing a highlystable non-active (weakly active) colloidal dispersion with a reactivitymodifier. Novel catalytic colloidal compositions prepared as abovecomprise stable colloids of non-precious or precious metals admixed witha reactivity modifier. The final admixture is thus comprised of at leasttwo distinct colloid stabilizers. The novel catalytic colloidalcompositions are utilized in the electroless plating process whichcomprises the steps of treating a dielectric substrate with the activecatalytic colloidal composition and then, when necessary, furthertreating the substrate with a reducing or activating composition toprovide additional active nuclei on the substrate surface, the activatedsubstrate then being contacted with an electroless plating bath. Whileit is generally preferred to admix the colloidal dispersion with thereactivity modifier, in an alternate approach the reactivity modifiermay be admixed with the primary stabilizer (which alone renders thecolloids weakly active) prior to the colloid nucleation process.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention is applicable to the metallicplating of dielectric substrates by autocatalytic (or as more commonlyknown, electroless) plating. Such processes are well known in the artand they produce a wide variety of products varying from printedcircuitry arrays, decorative plated plastic parts and magnetic tapes tometallized fibers.

The term "hydrous oxide" as used herein is intended to encompass theinsoluble oxides and insoluble hydroxides of metals. The preferablehydrous oxides are selected from the group consisting of oxides andhydroxides of cobalt, nickel, iron and copper and mixtures thereof.Other suitable hydrous oxides include oxides and hydroxides of preciousmetals such as palladium, silver and others.

It is also recognized that metallic colloids, (e.g. colloids of copperand nickel as well as alloys thereof) due to their pyrophoric natureoxidize when in contact with air and water. Therefore, they are reallymetallic nuclei with an outer oxidized surface and thus are alsoconsidered herein as hydrous oxide colloids. In addition, colloidalmetallic nuclei of precious metals, while they are more inert towardsoxidation, are also suitable in the practice of the present invention.

The term "stabilizer" as used herein is intended to encompass substanceswhich alter the characteristics of the colloid so as to prevent, delay,or minimize their coagulation and precipitation. It is believed thatthese stabilizers are adsorbed onto the surface of the colloids therebyaltering the surface charge and hence their stability. Stabilizerscontemplated by the present process and solution may include secondarycolloids (gelatin), dispersants, surfactants, sugars and polyalcohols(glycerol).

The term "surfactant" (or surface active agent) as used herein generallyrefers to substances which are capable of lowering the surface tensionof a liquid or the interfacial tension between two liquids. All usefulsurfactants possess the common feature of a water-soluble (hydrophilic)group attached to an organic (hydrophobic) chain. Surfactants as usedherein are also intended to encompass detergents, dispersants andemulsifying agents regardless of whether or not they lower the surfacetension of a liquid (e.g. water).

The term "reactivity modifier(s)" as used in the present inventiongenerally refers to substances which, while alone are generally inert,in said plating process promote activation of the otherwise weaklyactive colloids in the plating process (the catalytic preparation). Suchmodifiers may be of organic or inorganic nature as well as combinationsthereof. It should be recognized by those skilled in the art that thepreferred reactivity modifier composition to be added and the quantitythereof is best determined as a trial procedure for each stable colloidcomposition and/or substrate to be coated. Furthermore, it should berecognized that reactivity modifier(s) are also inherently colloidstabilizers. Thus, the selection for such potential members is endlessand should be obvious to one skilled in the art in view of the presentinvention.

I have also recognized that the primary stabilizer and/or the reactivitymodifier may be of an amphoteric (Zwitterion) nature. Such materialsthough they are neutrally charged are capable of yielding positively ornegatively charged functionality groups depending upon pH conditions.Hence it should be recognized that the inclusion of such materialsestablishes a simple way of obtaining either positively or negativelycharged colloids.

In general, the electroless plating process of the present inventioncomprises the steps of (1) contacting (priming) the substrate(preferably one which was previously cleaned and etched to promoteadhesion) with a colloidal catalytic composition, (2) developing oractivating the substrate further by contacting the substrate with areducing agent (or activating agent) to form a discontinuous layer ofthe metal either in a reduced oxidation state or in a more activated orconfiguration state, thus forming the catalytic nuclei active for theinitiation of the electroless plating (this step, however, may beoptional), and (3) contacting the substrate with a compatibleelectroless plating formulation. In step (2) it is recognized that anyof several chemical reactions may take place (e.g. dissolution orremoval of some of the colloidal stabilizer(s)), all of which provide amore active site with shorter induction time for the electroless platingprocess. It is also noted that generally speaking rinsing between stepsis considered good practice. In the above catalytic treatment, whenemploying colloidal dispersions comprising precious or non-preciousmetals in their elemental state, or alloys or compounds of said metals,sufficient activation of the substrate may be accomplished at thepriming step without requiring the additional activation with a separatereducing or activating composition prior to contacting the substratewith the electroless plating bath.

The following examples are illustrative of the concept of the presentinvention and are not to be taken as in limitation thereof; moreover, itshould be obvious to those skilled in the art that further optimizationis possible with respect to compositions and conditions indicated ashaving less than 100% coverage. Futhermore, it should be obvious thatthe present findings are not limited to the art of plating and they canbe used in other commercial fields requiring novel properties of thecolloids.

EXAMPLE 1

This example shows the general procedure of the novel electrolessplating process. Acrylo-nitryl-butadiene-styrene (ABS) substrates(Monsanto PG Grey-299) were etched in a solution comprising 400 g/l CrO₃and 350 g/l H₂ SO₄ (conc.) for about 10 minutes at 70° C. Thereafter,the etched substrates were immersed in a colloidal catalytic primersolution for about five minutes with said solution at 40° C. The primedsubstrates were then rinsed and immersed in a developer solutioncomprising 0.5 g/l NaBH₄ for a few minutes. The substrates were rinsedand then immersed in an electroless copper bath operating at 40° C. andhaving the following composition.

CuSO₄.5H₂ O: 15 g/l

EDTA (40%): 68 cc/l

NaOH: 9 g/l

NaCN: 3 ppm

Tergitol TMN: 0.2 (% wt.)

H₂ CO (37%): 22 cc/l

Final colloidal catalytic primer dispersion (working medium) was made bythe dilution of premade concentrated stock; the latter was generallyprepared via thermal aging or other equivalent conditions. While inthese examples substrates were pre-cleaned and etched using a wetchemical technique, other techniques of performing the preferred etchingwhich are of a dry nature may be substituted and used in accordance tothe present invention. A stabilized colloid (291 m) was prepared by theadmixing of 12.2 g/l Cu(NO₃)₂.3H₂ O, 12.2 g/l gelatin and sodiumhydroxide in an amount representing twice the molar concentration of thecopper ion. Prior to aging pH was adjusted to 9.0 and thereafter agingfor about 16 hours was undertaken at 75° C.

    ______________________________________                                               Final Composition of Relative (%)                                      No.    Colloidal Catalytic Primer                                                                         Plating Coverage                                  ______________________________________                                        1a     dilution (4×) of stock primer                                                                 0                                                       soln. with water                                                       1b     Same as above with 0.025M                                                                          100                                                      sodium lauryl sulfate                                                  1c     Same as 1a with 0.025M                                                                              95 (average)                                            sodium lauryl sulfate                                                  ______________________________________                                    

Using the same final composition of catalytic primer as in 1a and 1a butincluding 0.27 g/l of NaBH₄ gave a plating coverage of 0% and 75% formedia 1a and 1b respectively. While visually compositions 1a and 1bappeared the same, examination by an electron microscope at 150,000×showed a major difference in appearance. Specifically, the resultingcolloid 1b exhibited a finer particle size (almost an order ofmagnitude) compared to the colloids of 1a. Similar observations werealso noted in other cases. While I do not wish to be bound by theory, itis conceivable that the enhanced reactivity may be in part due to thisnoted change in particle size distribution. It should thus be recognizedin the optimization of the process and solutions, plating coverage isdependent upon the reducing medium reactivity (e.g. concentration),nature and amount of added reactivity modifier, as well as the amountand nature of colloid stabilizer used in the preparation of thestabilized colloid as well as nature and reactivity of the electrolessplating formulation.

EXAMPLE 2

It was also found that the present invention may be implemented in analternative sequence of steps. For example, solutions and substrateswere all the same as in Example 1 while the following key steps wereundertaken.

1. Immersion in the colloidal catalytic medium cited in Example 1, No.1a followed by a water rinse; then

2. Immersion for 5 minutes in a surfactant solution composed of 0.025 Msodium lauryl sulfate at 40° C. and rinse; then

3. Immersion for 5 minutes in 0.5 g/l NaBH₄ and rinse; finally

4. Immersion in the electroless copper formulation.

Results showed 90% metallic coverage. While the process shown in thisexample requires more steps in comparison to the process shown inExample 1, its adaptation falls within the spirit of this invention.Using the above surfactant prior to the immersion into the stabilizedcolloidal solution did not produce any perceptible plating results.

It should thus be recognized that in using the reactivity modifier, twobasic modes are possible. In the first mode the reactivity modifier isadmixed with the weakly active colloidal dispersion, while in the secondalternate mode it is used subsequent to the step of the weakly activecolloidal dispersion. Hence, as contemplated by the present inventor,both modes fall within the spirit of this invention.

EXAMPLE 3

Solutions, substrates and procedure were the same as in Example 1,except for the substitution of the following colloidal catalytic primer.

    ______________________________________                                                                      Relative (%)                                         Final Working Composition                                                                              Plating                                         No.  of Colloidal Catalytic Primer                                                                          Coverage                                        ______________________________________                                        3a   3.1 g/l protective colloid*                                                                             0                                                   0.005 M Cu.sup.+2                                                             pH final approx 9.0                                                      3b   Same as above with 0.025M                                                                              90                                                   Sodium dodecylsulfate (reactivity modifier)                              ______________________________________                                         *The protective colloid used is an extracted and refined collagen protein     and is designated as Fluid Colloid EX3 sold by the Swift Chemical Company     The concentrate stock dispersion was prepared under standard laboratory       conditions.                                                              

EXAMPLE 4

Catalytic solutions were prepared by the admixing of cobalt sulfate,water, a material(s) selected from lingosulfonates (derivative oflingnin) and sodium hydroxide. In a typical case (41-4) the catalyticsolution was comprised of

CoSO₄.7H₂ O: 14.3 g/l

dignosulfonate: 12.5 g/l

pH (after hydroxide addition) and aging): about 7.9

Dilution of above with water (1:9) and utilization in the presentprocess steps (as defined in Example 1) gave good metallic coverage.Similarly, nickel and copper catalytic solutions are prepared using anyof several soluble salts and hydroxides.

EXAMPLE 5

A procedure similar to Example 1 was used. However, sodium alphasulfonate was used as the reactivity modifier. Results showed a majorimprovement in the plating coverage.

EXAMPLE 6 (JP-70)

A procedure similar to Example 1 was used. However, a commercialalkaline electroless copper bath comprising formaldehyde was used atroom temperature. The weakly active (control JP-39) colloid comprisedthe following admixture with some thermal energy added.

CuSO₄.5H₂ O: 10.1 g/l

Gum Arabic: 12 g/l

NaBH₄ : 1.5 g/l

NaOH: 1.6 g/l

Using the control followed by a rinse in 0.5 g/l NaBH₄ gave at best 50%metallic coverage. However, incorporating a sodium salt of polymerizedalkyl naphthalene sulfonic acid at a concentration of 3.6 g/l to controlresulted in 100% coverage.

EXAMPLE 7 (JP-84)

Control colloidal composition and procedure were the same as in Example6. To the control 4 ml/l of absolute methanol was added as thereactivity modifier. Plating results after the incorporation of thereactivity modifier were 100% in coverage.

EXAMPLE 8 (CB-10)

A control (CB-10) colloidal composition comprised the admixture of:

CoCl₂.6H₂ O: 2.4 g/l

CuSo₄.5H₂ O: 10.1 g/l

Gum Arabic: 12 g/l

NaBH₄ : 1.9 g/l

NaOH: 2.0 g/l

The composition was mixed with added thermal energy.

0.96 g/l of dioctyl sodium sulfosuccinate was incorporated to thecontrol. Using 0.3 g/l of dimethylamine borane (at 45° C. for 3 minutes)showed a significant improvement in the plating results. In this exampleI found that the combination of copper and cobalt results in areactivity level superior to that of either metal alone. Furthermore, Ifound that the optimum cobalt to copper ratio must be determined foreach individual composition; this can be accomplished by simpleexperiments obvious to those skilled in the art. In addition, while thisphenomenon is not completely understood, it is anticipated that nickeland/or iron may be substituted for the cobalt since they are similar intheir electronic structure.

In general it was found that an excess of copper to cobalt (or nickel)is preferred.

EXAMPLE 9

A colloidal dispersion of the admixture at a pH of 12.7 was preparedwherein the reaction was carried out above room temperature.

CuSO₄.5H₂ O: 9.96 g/l

CoCL₂.6H₂ O: 2.38 g/l

NaOH: 7.52 g/l

NaBH₄ : 0.71 g/l

Sodium lignosulfonate: 12.0 g/l

The resulting dispersion was tested in accordance with the procedure ofexample 8. Results showed no plating. However, using the samecomposition with acid addition (e.g. sulfuric acid) to a final pH valueof about 7.53 resulted in 100% metallic coverage. Accordingly, it shouldbe recognized that pH adjustment(s) and, hence, those chemicaladditive(s) which are used to acheive said pH adjustment(s) arereactivity modifier(s) and their utilization falls within the spirit ofthis invention.

EXAMPLE 10

A composition similar to that in Example 9 at a pH of 7.47 with added0.2 g/l of mercaptobenzothiazole was tested, followed by 0.1 g/ldimethylamine borane (at 45° C.) solution. Whereas the control plated20% metallic coverage at best, the modified composition gave a platingcoverage of 90 to 100%. The above testing was done at a pH of about 7.5.

It is noted that while in most cases the reactivity modifier was addedafter the colloid was formed, the invention is not limited to thissequence but is rather aimed at the final composition in which all thecomponents including reactivity modifiers are present.

While it is generally preferred to admix the weakly active colloidaldispersion with the reactivity modifier, in an alternate approach thereactivity modifier may be admixed with the primary stabilizer (whichalone renders the colloids weakly active) prior to the colloidnucleation process.

EXAMPLE 11

A colloidal composition was prepared using the following chemicals. Thecolloidal phase was nucleated at about 55° C. In this composition, asdiscussed in a copending application, it is believed that a copper-tininteraction product is formed Final pH was adjusted to 5.0.

CuCl₂ : 0.04 M

Sn(BF₄)₂ : 0.081 M

NaBH₄ : 0.076 M

NaOH: 0.37 M

Gelatin: 6 g/l

Daxad CP-1 (T.S. 34.4%)*: 0.1 ml/l

Comparison of the resulting product and the same without the CP-1 showedthe former to have a greater activity as reflected in the adsorptiononto an alumina ceramic substrate. The CP-1 (or reactivity modifier) wasadded along with the gelatin prior to the colloid formation.

From the above variety of reactivity modifiers used, it should beevident that the invention is not intended to be limited to any specificchemical class, but rather includes all materials which function aseither stabilizer and/or adsorbants onto the colloid nuclei.

While I do not wish to be bound by theory, the following model isproposed for possible account of the phenomenon at hand. In theformation of highly stabilized colloidal dispersions, the colloidalnuclei (e.g. hydrous oxide of copper) are surrounded by a stabilizer(s)which is adsorbed onto said nuclei. It is probably the degree ofadsorption and its consequent charge modifications which contribute tothe stabilization mechanism and at the same time make the colloidalnuclei sterically impervious to the chemical reaction with subsequentreducing agent, or a key component within the electroless plating bath,especially when the latter are used in moderate reactivity (e.g.,concentration of said reducing agent) required for economical platingprocesses.

Upon the transformation of the weakly active colloids, some removal ofstabilizer(s) from the adsorbed layer takes place by a displacementreaction making the colloid nuclei more accessible to subsequentinteraction with the reducing medium and hence increasing its reactivityin the plating process. It also appears that in some cases the weaklyactive colloids are transformed to particles of smaller size.

It should be understood that although the term colloid stabilizer refersto various chemical compounds, the effectiveness of stabilizers is notnecessarily the same. Thus a stabilizer in one system may be areactivity modifier in another system.

Schematically, the following simple equilibrium reaction may representthe present findings ##STR1## in which ads denotes adsorbant; n, m, xdenotes some value. x could range from zero to some value. Also ads₁ andads₂ are chemically distinguishable. State A is a less reactivecolloidal dispersion relative to State B. As aforesaid, the presentinvention is not bound to the proposed model and furthermore, in any ofthe states shown there may be more than one adsorbant as well as amultiplicity of colloids, having different metallic nature and/ormorphology and/or of compounds and/or of alloys.

It should be recognized that the present invention is not limited to thenature or specific reducing agent used in the process of plating.Moreover, this invention is also not limited to the use of a reducingagent in the developing or activating step of the procedure. It shouldalso be obvious to those skilled in the art that compatible electrolessformulations should be selected.

It has also been recognized that in using the processes according toU.S. Pat. No. 3,993,799 or 3,993,491 or that of U.S. Pat. Nos. 3,772,056and 3,772,078, some contamination of the reducing medium would takeplace with time. The nature of the contamination may be either ionic orcolloidal as well as combination thereof. It is further recognized thatsuch combinations would tend to interact with the reducing mediumaccounting for some undesired homogenous decomposition.

It is therefore highly desireable to insure that such homogeneousdecomposition catalyzed by metallic impurities be minimized. In meetingthis objective it is proposed that selective additives in controlledconcentrations be incorporated in the reducing medium. Specifically,chelating (or complexing) agents should be incorporated for thecomplexion of metallic ions while strong colloidal stabilizers should beincorporated in the encapsulation of colloidal particles and henceresult in their deactivation. It may further be necessary to add acombination of both types of materials. In introducing such materials(stabilizers), caution ought to be exercised in insuring that thereduction process is not disturbed. Thus, the concentration of saidstabilizers should be controlled. The selection of potential colloidstabilizers should be evident from the present invention. For purposesof clarification, stabilizers incorporated in the reducing solutions aretermed deactivators. Based upon the present teachings, it should beobvious that any of several electroless plating compositions may besubstituted and used.

As heretofore pointed out, the modification of reactivity in accordancewith the invention at times results in a substantial reduction ofcolloid particle size. This in and of itself has uses other than inelectroless plating (for example, as a thermal heat transfer compositionwhich is particularly useful in solar energy convertors). Thecomposition may be used with or without the added reactivity modifier.

In nucleating the colloids, soluble and insoluble compounds may be usedas the starting compounds for the synthesis of the insoluble (colloidal)phase; the final working composition may then be in a suitable solvent.

What I claim is:
 1. A process for the electroless or chemical plating ofa non-conductor substrate comprising the steps;(1) etching saidsubstrate, (2) contacting said substrate with an activated colloidaldispersion wherein said colloidal dispersion comprises a metal which inone of its oxidation states is capable of electroless or chemicalplating initiation, and wherein said metal may be in an elemental state,or an alloy, or compound, and mixtures thereof and further wherein saidactivated colloidal dispersion comprises at least one primary stabilizerwhich alone renders the colloidal dispersion weakly active and at leastone reactivity modifier and wherein said primary stabilizer and saidreactivity modifier are inherently colloid stabilizers however they aredifferent materials, and (3) contacting the treated substrate with acompatible electroless plating bath for the deposition of a metal. 2.The process according to claim 1 wherein said primary stabilizer is asecondary colloid.
 3. The process according to claim 1 wherein theprimary stabilizer and the reactivity modifier are admixed prior to thecolloid nucleation process.
 4. The process according to claim 1 whereinsaid metal is selected from the group consisting of copper, cobalt,nickel, palladium and iron.
 5. The process according to claim 1 whereinsaid activated colloidal dispersion is positively charged.
 6. Theprocess according to claim 1 wherein said activated colloidal dispersionis negatively charged.
 7. The process according to claim 1 furthercontaining the step of activation and wherein the step of activationreduces the induction time prior to metal deposition.
 8. The processaccording to claim 1 wherein said primary stabilizer is an amphotericcompound.
 9. The process according to claim 1 wherein said reactivitymodifier is an amphoteric compound.
 10. The process according to claim 1wherein said reactivity modifier is a surfactant.
 11. The processaccording to claim 1 wherein said electroless plating bath is copper.12. The process according to claim 1 wherein said colloid comprisescopper in a reduced oxidation state.
 13. The process according to claim1 wherein said activated colloidal dispersion comprises water.
 14. Theprocess according to claim 1 wherein said substrate is a printedcircuitry type substrate.
 15. The process according to claim 1 whereinsaid colloidal dispersion comprises a colloidal product of copper andtin.
 16. The process according to claim 1 wherein said activatedcolloidal dispersion comprises copper and wherein said copper is in anelemental state.
 17. The process according to claim 1 further containingthe step of water rinsing and wherein said rinsing follows the etchingof said substrate.
 18. The process according to claim 1 wherein saidcolloidal dispersion is derived through the nucleation reaction startingwith compound(s) which are soluble in a solvent.
 19. The processaccording to claim 1 wherein said colloidal dispersion is derived fromthe nucleation reaction and further wherein the starting compound(s) areinsoluble in a solvent.
 20. The process according to claim 1 whereinsaid electroless plating is part of a printed circuitry through-holemetallization.